Cancer is the second leading cause of death in the United States. Over one million people develop cancer each year, and approximately half of all men and one third of all women in the United States will develop cancer during their lifetimes.
Prostate cancer is the second most common type of cancer found in American men (after skin cancer), and the second-leading cause of cancer death (after lung cancer). The American Cancer Society (ACS) estimates that 1 in 6 men will develop prostate cancer in his lifetime and 1 in 34 men will die of the disease. The ACS further estimates that there will be about 218,890 new cases of prostate cancer and about 27,050 deaths attributable to prostate cancer in the United States in 2007.
Most cancers, including prostate cancer, are frequently treated by a combination of approaches, including surgical removal of a tumor, chemotherapy, and/or radiation therapy. Surgical procedures are usually not sufficient to remove a tumor in its entirety, so surgery is frequently accompanied by chemotherapy and/or radiation therapy. Chemotherapy involves the use of drugs to kill tumor cells, and radiation therapy involves treatment with high-energy rays (e.g. x-rays) to kill or shrink tumor cells.
Unfortunately, however, chemotherapy and radiation cause serious and sometimes life-threatening side effects, including fatigue; nausea; vomiting; pain; hair loss; anemia; central nervous system problems; infection; blood clotting problems; mouth, gum, and throat problems; diarrhea; constipation; nerve and muscle effects; kidney and bladder effects; flu-like symptoms; fluid retention; and effects on sexual organs.
Chemotherapy causes such severe side effects because the treatment involves the systemic administration of cytotoxic agents to a patient. These agents cannot distinguish tumor cells from normal cells and, therefore, kill healthy cells as well as tumor cells. Side effects are worsened because a very large dose must be administered to the patient in order to deliver a therapeutically effective dose to a tumor site. Although radiation therapy is administered somewhat more locally than chemotherapy, radiation treatment still results in the destruction of normal tissue in the vicinity of the tumor.
Thus, targeting of a therapeutic agent (e.g., to a particular tissue or cell type; to a specific diseased tissue but not to normal tissue; etc.) is desirable in the treatment of tissue specific diseases such as cancer (e.g. prostate cancer). For example, in contrast to systemic delivery of a cytotoxic anti-cancer agent, targeted delivery could prevent the agent from killing healthy cells. Additionally, targeted delivery would allow for the administration of a lower dose of the agent, which could reduce the undesirable side effects commonly associated with traditional chemotherapy.
Therefore, there is a strong need in the art for systems for selectively delivering therapeutic agents to desired tissues or cells. There is a further need for systems for targeting the delivery of cytotoxic anti-cancer agents to tumors, such as tumors associated with prostate cancer. The ability to control the precise level and location of a therapeutic agent in a patient would allow doses to be reduced, minimize side effects, and open new avenues for “personalized” therapy.